Explanation:
why ? you did it right there already.
the numerator is the top part of the fraction, the "counting" part (how many units of a certain type or size are there).
the denominator (the bottom part) is defining the type or size of units described by the fraction.
so, we are adding 4 to the numerator of 2/5, making it (2+4)/5 = 6/5
what do we need to add to the denominator (the bottom part) to make the fraction have the value of 1/2 ?
so, what x would make 6/x = 1/2 ?
6 = x/2
x = 6×2 = 12
so, we need to get 12 in the denominator, where we have currently 5.
therefore, we need to add 12-5 = 7 to it.
so that
6/(5+7) = 6/12 = 1/2